Alloy cast iron



Patented July 25, 1939 PATENT OFFICE "ALLOY CAST nioN Edwin A. Jones,Jacksomand Arthur H. v

Ohio, assisnors to Globe Iron Com Columbus,

Dierker,

pany, Jackson, Ohio, a corporation No Drawing. Application March 23,1938, Serial No. 197,726

4 Claims.

Our present invention relates to an improvement in alloy cast iron, inwhich silicon and chromium are the principal alloying agents, and inwhich the silicon, in the various proportions in 5 which it may be usedwith reference to the chromium, is always in substantial excess of thechromium content.

We have'found that alloys prepared in accordance with our invention,have high wear and heat-resisting properties, and exhibit unusual vatedtemperatures. 4

We have further found that such alloy cast irons are machinable at-Brinell hardness far in excess of that at which cast irons or steels areconsidered to be unmachinable.

Further, our alloy cast iron can be produced from low cost materials,'in furnaces of "the cupola type, which are recognized as, being thelowest cost type of furnace in common use today, and by labor which doesnot require to be highly skilled.

Cast iron is generally considered to contain the following materialssubstantially within the ranges indicated, namelyresistance toscaling.,warping and growth at ele- Per cent Total carbon 2.50 to 3.70

. sn'im'n .80 to 3.00 Manganese .40 to 1.20 Sulphur Under 0.20Phosphorus Under 1.00

Where any of the elements exceed the maximum amounts indicated, theexcess of the 3:; amount of such element usually required to produce aniron of normal properties, is considered an alloying element.

In the alloy cast iron of our invention, weuse silicon in excess oftheamount required to pro- 40 duce a good quality of cast iron, as analloying agent to secure properties not found in unalloyed irons, and wealso use chromium as an alloying agent, but in the compositions of ouralloy we maintain the silicon content always in excess of the chromiumcontent by a substantial amount. Despite its hardness, our'alloycontains as cast free carbon in the form of graphite flakes or nodules,and is thus definitely not a steel, and should not be confused withsteels containing silicon and chromium.

With the foregoing explanation in-mind-, one of the principal objects.of our invention is to provide an alloy cast iron havin h W and heatresisting properties and unusual, resistance to scaling, warping andgrowth at elevated tem-t 5 Deratures. 1 a

A further object is to provide an alloy cast iron of great hardness,which is machinable at unusually high Brinell hardness, and without theuse of lubricants.

A further object is to provide an alloy cast iron comprising silicon andchromium as the principal alloying agents. with the silicon in excess ofthe. chromium, and having .free graphite, the alloy being characterizedby high resistance to wear, 15 and to scalingpwarpingand growthlatelevated temperatures, and being machinable at hardnesses far beyondthose of cast-irons.

Still another object of .our invention is to provide an alloy cast ironof thecharacteristics set 20 forth above, and having a relatively lowmelting point and .low shrinkage characteristics, such that goodcastings of intricate and thin sections can be produced with ordinaryfoundry facilities.

A further object is to provide an alloy cast iron having the variousqualities and characteristics referred to, which is capable ofproduction in cupola furnaces at relatively low cost, and withoutrequiring labor of anything more than ordinary skill. I I

In producing our alloy cast iron, we prefer that it contain constituentswithin the following table, ,namely-- I While the percentages of thevarious materials within the ranges indicated may vary, in all cases wekeep the silicon content in excess of the chro- 4 5 mium by asubstantial amount. The presence of the relatively high silicon contentwith regard to the chromium in our alloy, we believe, lowers the,solubility of the carbon in the iron at room temperatures, andhence, asthe iron cools ,from

' tributed substantially uniformly the molten condition, carbon isprecipitated from solution in the form of graphite, which isdisthroughout the body. of the metal in the form of small flakes ornodules.

The alloy can be produced from relatively low cost raw materials and insimple and economical types of melting units, by workmen of no more thanordinary skill. As illustrative, alloy steels require for theirproduction, the use of the-electric furnace, the open hearthfurnace, orthe crucible furnace. All of these types of furnaces are expensive tobuild, maintain and operate. Our alloy, on the other hand, can beproduced in the cupola type furnace which, as recognized in theindustry, is the type of furnace which is the cheapest per unit ofcapacity, in common use. It is not only less expensive in initial cost,than the other types of furnaces referred to, but is also cheaper tomaintain and operate.

Examples of a number of compositions of our alloy are given in thetables which follow, in which tables various specimens have been testedagainst other cast irons.

We give below some results of wear tests, as well as tests of otherphysical properties, and .a few compositions of the alloy of ourinvention. The wear tests were made by holding the specimen under aweight of 1380 grams on they table of a Dorry machine, a. constantstream of washed silica sand being fed to test. At the end of 6000revolutions, the specimen was moved and weighed, and the weight loss dueto wear was noted. The physical properties were determined by standardA. F. A. methods.

Specimen No 7i 2352 i 2395 2423 2423 Analysis:

'I. C 3.30 3.10 2. 52 3.17 2. 21 Heat Si 2.40 1.73 4. 23 3.05 5.30treated Mn .65 .94 .60 .50 .63 P. .18 .16 .11 .056 .084 S .11 13 .065.065 .052 Or 2.20 .96 2. 98 Brinell hardness Noun 179 217 255 255 341388 Transverse strength pounds 2, 560 3, 230 2,950 3,290 2,120Deflection inches 292 270 190 282 137 Tensile strength lbs. per sq. in.29, 200 43, 000 34, 700 42, 800 32, 000 43,000 Wear s grams.. 5.19 3.851.931 2.07 1.67

is of the same composition as the specimen of that same number in thetable, but not designated as heat-treated. The heat treatment consistedof normalizing at 1800 deg. F. and drawing at 1300 deg. F.

The above data shows that the alloy iron, despite its high hardness, hasstrength and toughness comparable to a good grade of high test iron.

A remarkable feature of our alloy is that it can be machined atunusually high Brinell hardness. Cast iron is ordinarily consideredunmachinable when it has a Brinell hardness of more than 280. All of thegiven examples of our al- 10y, however, even though they tested up to388 Brinell, were readily machinable, and indeed, we havemachinedspecimens of our alloy having a Brinall hardness of 415.

The superior resistance of our alloy to growth the table during thetance,

Specimen No 1343 219-6 'l. 2.80 3.44 Si 2.30 2.25 Mn .37 .53 .56 P .05.27 .43 S .02 .08 .06 CL. 4.16 Scale loss .percent. 2.00 8.87 10.70Growth percent 07 1. 74 5. 82

In this table, specimen 1343 isan alloy of our invention, while specimen219-6 is a high strength cast iron, and specimen 116-1 is a soft castiron. The scale loss. and the growth of our alloy are both remarkablylow, as indicated in the table.

In addition to the qualities of unusual high hardness, and high wear andheat-resistance, our alloy exhibits the further quality of relativelysmall shrinkage during solidfication of the metal I from the moltenstate, and in addition, has a melting point very much lower than alloysteels. Hence the alloy possesses excellent casting properties, suchindeed, that with ordinary foundry facilities, sound castings ofintricate and thin sections can be made.

We areawarethat steels containing silicon and chromium are known in theart, but our alloy possesses characteristics which distinctlydifferentiate it from such steels, such for inas its low productioncost; its machinability; its silicon content in excess of the chromium;and its brittleness as compared to workability of steel; also ease ofcasting to shape as compared to steel. i

On the other hand, the ability of our alloy to be machined at Brinellhardness far greater than that of cast irons, and its unusually highheat resistance and wear resistance, give it qualities unpossessed bycast irons heretofore known in the art with which we are acquainted.

It will be understood that our alloy may be heat-treated subsequent tocasting by one of the accepted methods for ferrous alloys; i. e.,annealing, either at a temperature above or below the critical;normalizing from -a temperature above or below the critical; quenchingfrom a temperature above the-critical and drawing at some suitabletemperature below the critical.

While the foregoing description sets out a number of specificembodiments of our invention, it will be understood that various changesin proportions of the elements constituting our alloy may be made withinthe scope of the appended claims. It will further be understood that theforegoing for purposes of'illustration of our invention,and that noundue limitations should be deduced therefrom, but that the claimsshould be broadly construed within the limitations of the prior art.

Having thus described our invention what we claim as new and desire tosecure by United States Letters Patent is:

1. An alloy cast iron, having silicon in proportions greater thanchromium, and in which a substantial part of the carbon is in the formdescription has been given 1 about .11%; sulphur of free graphite, saidalloy containing silicon 4.23% to 10.00%; chromium 0.6% to 8.00%;manganese 0.20% to 3.00%; phosphorus under 0.30%; sulphur under 0.20%;carbon 1.80% to 3.20%, and the balance iron.

2. An alloy cast iron containing silicon about 4.23%; manganese about50%; phosphorus about .065%; chromium about 2.20%, total carbon about2.50%, and the balance iron, said alloy being characterized by high wearand heat resistance.

3. An alloy cast iron containing silicon about 5.30%; manganese about.63%; phosphorus 5.73% manganese about 084%; sulphur about .o52%-;chromium about 2.98%, total carbon about 2.20%, and the balance iron,said alloy being characterized by high wear and heat resistance.

4. An alloy cast iron containing silicon about about .37 phosphorusabout 0.05%; sulphur about .02%; chromium about 4.16%,total carbon about2.13%, and the balance iron, said alloy being characterized by high wearand heat resistance.

EDWIN A. JONES. A. H. DIERKER.

